Log 99 is a preconfigured memory-based log that logs events from the main event source (not security, debug, and so on). Log 99 exists by default.
ALA-1>config>log# info detail
#------------------------------------------
echo "Log Configuration "
#------------------------------------------
...
snmp-trap-group 7
exit
...
log-id 99
description "Default system log"
no filter
from main
to memory 500
no shutdown
exit
----------------------------------------------
ALA-1>config>log#